Chapter 28.5 Adaptive Immunity

This textbook is designed specifically for Kansas State's Biology 198 Class. The course is taught using the studio approach and based on active learning. The studio manual contains all of the learning objectives for each class period and is the record of all student activities. Hence, this textbook is more of a reference tool while the studio manual is the learning tool.
Authors: Robert Bear, David Rintoul, Bruce Snyder, Martha Smith-Caldas, Christopher Herren, and Eva Horne
Kansas State University Libraries
New Prairie Press
Bear, Robert; Rintoul, David; Snyder, Bruce; Smith-Caldas, Martha; Herren, Christopher; and Horne, Eva, "Principles of Biology" (2016). Open Access Textbooks. 1. https://newprairiepress.org/textbooks/1
The textbook was originally published and is also available to download at http://cnx.org/contents/[e-mail] is licensed under a Creative Commons Attribution License 4.0 license.

Episode Transcript

(00:00):
Welcome to Principles of Biology. Thisbook was written by the Open Alternative Textbook
Initiative at Kansas State University and isbeing released as a podcast and distributed under
the terms of the Creative Commons AttributionLicense. Today's episode is chapter twenty eight
point four Innate Immunity. All hyperlinks, images, and sources can be found

(00:21):
at the link to the book.In the description, the organism possesses certain
contrivances, by means of which theimmunity reaction, so easily produced by all
kinds of cells, is prevented fromacting against the organism's own elements, and
so giving rise to autotoxins. Thesecontrivances are naturally of the highest importance for
the existence of the individual. PolarlicGerman Immunologist and Pharmacologist on Humoisins nineteen o

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one. Although other organisms have immuneresponses of various types, the vertebrate immune
system is the most sophisticated. Thevertebrate immune system is a complex, multilayered
system for fending against external and internalthreats to the integrity of the body.
The system can be divided into twotypes of defense systems. The innate immune
system, which is non specific towarda particular kind of pathogen, and the

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adaptive immune system, which is specificfigure. Innate immunity relies on physical and
chemical barriers that work on all pathogens, sometimes called the first line of defense.
The second line of defense of theinnate system includes chemical signals that produce
inflammation and fever responses, as wellas mobilizing protective cells and other chemical defenses.

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The adaptive immune system mounts a highlyspecific response to substances and organisms that
do not belong in the body.The adaptive system takes longer to respond and
has a memory system that allows itto respond with greater intensity should the body
re encounter a pathogen even years later. That memory is the basis for the
long term effectiveness of many vaccines.Table shows vertebrate immunity. Two columns for

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innate and adaptive immune system characteristics.The innate immune system if further divided into
physical barriers and internal defenses. Underphysical barriers are skin hairs, cilia,
mucous membranes, mucus, and chemicalsecretions digestive enzymes in mouth and stomach acid
Under internal defenses are inflammatory response complementproteins, phacacidic cells and natural killer in

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K cells. In the adaptive immunesystem columner antibodies, and the humoral immune
response, cell mediated immune response,and memory response. There are two main
parts to the vertebrate immune system.The innate immune system, which is made
up of physical barriers and internal defenses, responds to all pathogens. The adaptive

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immune system is highly specific external andchemical barriers. The body has significant physical
barriers to potential pathogens. The skincontains the protein keratin, which resists physical
entry into cells. Other body surfaces, particularly those associated with body openings,
are protected by the mucous membranes.The sticky mucus provides a physical trap for

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pathogens, preventing their movement deeper intothe body. Some openings of the body,
such as the nose and ears,are protected by hairs that catch pathogens,
and the mucous membranes of the upperrespiratory tract have sillia that constantly sweet
pathogens trapped in the mucous code upto the mouth. The skin and mucous
membranes also create a chemical environment thatis hostile to many micro organisms. The

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surface of the skin is acidic,which prevents bacterial growth. Saliva, mucus,
and the tears of the ike containan enzyme that breaks down bacterial cell
walls. The stomach secretions create ahighly acidic environment, which kills many pathogens
entering the digestive system. Finally,the surface of the body in the lower

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diges jestive system have a community ofcommensal microorganisms such as bacteria, archaea,
and fungi the microbiome that coexist withoutharming the body. There is evidence that
these organisms are highly beneficial to theirhost, combating disease causing organisms and outcompeting
them for nutritional resources provided by thehost body. Despite these defenses, pathogens

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may enter the body through skin abrasionsor punctures, or by collecting on mucosal
surfaces in large numbers that overcome theprotections of mucus or cilia internal defenses.
If pathogens defeat these defenses and enterthe body, the innate immune system responds
with a variety of internal defenses.These include the inflammatory response, phagocytosis,

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natural killer cells, and the complementsystem. White blood cells in the blood
and limph recognize pathogens as foreign tothe body. A white blood cell is
larger than a red blood cell,is nucleated and is typically able to move
using ameboid locomotion. Because they canmove on their own, white blood cells
can leave the blood to go toinfected tissues. For example, a monocyte

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is a type of white blood cellthat circulates in the blood and lymph and
develops into a macrophage after it movesinto infected tissue. A macrophage is a
large phacacidic cell that engulfs and devoursforeign particles and pathogens. Once a pathogen
is recognized as foreign and devoured bya macrophage, chemicals called cytokines are released.

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A cytokine is a chemical messenger thatregulates cell differentiation, form and function,
proliferation production, and gene expression toproduce a variety of immune responses.
Approximately forty types of cytokines exist inhumans. In addition to being released from
white blood cells after pathogen recognition,cytokines are also released by the infected cells

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and bind to near by uninfected cells, inducing those cells to release cytokines.
This positive feedback loop results in afirst of cytokine production. One class of
early acting cytokines is the interferons,which are released by infected cells as a
warning to near by uninfected cells.An interferon is a small protein that signals

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a viral infection to other cells.The interferons stimulate uninfected cells to produce compounds
that interfere with viral replication. Interferonsalso activate macrophages and other cells. The
inflammatory response and phagocytosis the first cytokinesto be produced in courage. Inflammation a
localized redness, swelling, heat,and pain. Inflammation is a response to

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physical trauma, such as a cutor a blow, chemical irritation, and
infection by pathogens, viruses, bacteria, or fungi. The chemical signals that
trigger an inflammatory response enter the extracellularfluid and cause capillaries to dilate, expand,
and capillary walls to become more permeableor leaky. The serum and other

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compounds leaking from capillaries caused swelling ofthe area, which in turn causes pain.
Various kinds of white blood cells areattracted by the cytokines released at the
area of inflammation. The types ofwhite blood cells that arrive at an inflamed
sight depend on the nature of theinjury or infecting pathogen. For example,
a neutrophil is an early arriving whiteblood cell than engulfs and digest pathogens.

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Neutrophils are the most abundant white bloodcells of the immune system. Figure.
Macrophages follow neutrophils and take over thephagocytosis function and are involved in cleaning up
cell debris and pathogens. Illustration showsa capillary near the surface of skin that
has a cut in it. Bacteriahave penetrated the skin around the cut.

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In response, mass cells in thelower part of the skin tissue release histamines
and dendrid it cells release cytokines.The histamines cause the capillary to become permeable.
Neutrophils and monocytes exit the capillary intothe damaged skin. Both the nutrophil
and macrophage release cytokines and consumes bacteriaby phagocytosis. White blood cells leukocytes release

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chemicals to stimulate the inflammatory response followinga cut in the skin. Cytokines also
send feedback to cells of the nervoussystem to bring about the overall symptoms of
feeling sick, which include lethargy,muscle pain, and nausea. Cytokines can
thus increase the core body temperature,causing a fever. The elevated temperatures of

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a fever inhibit the growth of pathogensand speed up cellular repair processes. For
these reasons, suppression of fevers shouldbe limited to those that are dangerously high.
Natural Killer cells a lymphosyte is awhite blood cell that contains a large
nucleus figure. Most lymphocytes are associatedwith the adaptive immune response, but a

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class of lymphocytes known as natural killercells are part of the innate immune system,
like other white blood cells that attackinvading bacteria or fungi. Natural killer
K cell is a lymphocyte. Naturalkiller cells kill body cells that are infected
with viruses or cancerous cells. Encasecells identify intracellular infections, especially from viruses,

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and attack the infected cells, destroyingthem so that they cannot release more
viruses. Micrograph shows a round cellwith a large nucleus occupying more than half
of the cell. Lymphocytes such asENC cells are characterized by their large nuclei
that actively absorb right stain and thereforeappear dark colored under a microscope. Credit

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scale bar data from Matt Russell.Illustration shows several innate immunity cells. MAST
cells have an abundance of cytoplasmic granulesand an irregular nucleus. Natural Killer cells
and neutrophiles are filled with granules.Neutrophiles have a multilobed nucleus. Macrophages are
irregular in shape with around nucleus.Cells involved in the anatomine response include mast

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cells, natural killer cells, andwhite blood cells such as monocytes. Macrophages
and neutrophils complement an array of approximatelytwenty types of proteins called a complement system,
is also activated by infection or theactivity of the cells of the adaptive
immune system, and functions to destroyextracellular pathogens. Liver cells and macrophages synthesize

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inactive forms of complement proteins continuously.These proteins are abundant in the blood serum
and are capable of responding immediately toinfecting microorganisms. The complement system is so
named because it is complementary to theinnate and adaptive immune system. Complement proteins
bind to the surfaces of microorganisms andare particularly attracted to pathogens that are already

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tagged by the adaptive immune system.This tagging involves the attachment of specific proteins
called antibodies discussed in detail later tothe pathogen. When they attach, the
antibodies change shape, providing a bindingsite for one of the complement proteins.
After the first few complement proteins bind, a cascade of binding in a specific

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sequence of proteins follows, in whichthe pathogen rapidly becomes coded in complement proteins.
Complement proteins perform several functions, oneof which is to serve as a
marker to indicate the presence of apathogen to phacacidic cells and enhance engulfment.
Certain complement proteins can combine to openpores in microbial plasma membranes, causing ion

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leakage and lysis of the microbial cells. This podcast will be released episodically and
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